Looks like they changed the default behavior of the ctrl+shfit+t keybinding in recent versions to reopen the last tab closed (like many browsers support). To view your current Keyboard Bindings, select the following menu option:

File > Preferences > Keyboard Shortcuts

If you want to change the ctrl+shfit+t keybinding back to issuing your default test task, simply change the value of the command property in the following object: